Removable cassette for an apparatus for sampling nanoparticles present in an aerosol, and filtration assembly for such a casette

ABSTRACT

The invention relates to a filtration assembly (5) comprising an annular support (12) which comprises an annular step (13) having an apex on which a filter membrane (11) rests, and a cover (20) covering the annular support in order to hold a periphery of the membrane between the cover and the annular support. The cover comprises a ring (21) which fits around the step to trap the periphery of the membrane between the ring and the annular support, the ring being extended by a skirt (22) which extends as a projection from the ring to cover an external peripheral wall of the annular support and to exhibit an end face (23) which extends in continuity with a bearing face (24) of the annular support. The invention also relates to a removable cassette for an apparatus for sampling nanoparticles comprising such a filtration assembly.

The invention relates to a removable cassette for an apparatus forsampling nanoparticles present in an aerosol, and to a filtrationassembly for such a cassette.

BACKGROUND OF THE INVENTION

Document FR3022025 discloses a nanoparticles-sampling apparatus equippedwith means for sucking in an aerosol, and to which there is attached aremovable cassette that forms a tunnel with an inlet open to the outsideand an outlet that can be fitted with a fluidtight seal to a suctioninlet of the sampling device. The tunnel is barred by a filtrationassembly such that the aerosol drawn in by the tunnel passes through thefilter of the filtration assembly. This filter halts and retains thenanoparticles of the sucked-in aerosol that passes through the tunnel.

The removable cassette comprises a base comprising means of attachmentto the sampling apparatus, and a cap attached to the base to trap thefiltration assembly between the base and the cap. The filtrationassembly comprises an annular support formed as one material with thefilter itself. The tunnel is sealed by a flat seal interposed betweenthe annular support and the base.

For industrialization reasons it is envisioned to use a filtrationassembly like the one illustrated in document FR2992227. That filtrationassembly comprises a filter membrane borne by an annular supportcomprising a peripheral step on the apex of which the filter membranerests. The annular support is covered by a ring that can be slippedaround the step to sandwich the periphery of the filter between the ringand the support and thus pull the membrane taut so that it exhibits aplanar wall suitable for analysis purposes.

It is important to ensure that no passage is able to form a bypassallowing the sucked-in aerosol to avoid passing through the filter, orallowing it to pass through the filter but without coming from the entryto the tunnel, for example by slipping in through a passage between thebase and the cap of the cassette.

SUBJECT OF THE INVENTION

It is an object of the present invention to propose a particular layoutof the constituent components of the removable cassette that improvesthe efficiency and reliability of the sample taking and makes thefiltration assembly easier to handle.

DESCRIPTION OF THE INVENTION

In order to achieve this objective the invention first of all proposes afiltration assembly for halting and retaining nanoparticles insuspension in an aerosol passing through the filtration assembly, thefiltration assembly comprising an annular support which comprises anannular step having an apex on which a filter membrane rests, and acover covering the annular support to hold a periphery of the membranebetween the cover and the annular support. According to the invention,the cover comprises a ring that can be slipped around the step tosandwich the periphery of the membrane between the ring and the annularsupport, the ring being extended by a skirt which projects out from thering to cover an external peripheral wall of the annular support and tohave an end face which extends in continuity with a bearing face of theannular support.

The skirt performs a number of functions:

-   -   it helps to seal the cassette. Specifically, before such a        filtration assembly is placed in a removable cassette so that it        can be sandwiched between the base and the cap of the cassette,        all that is required is to fit a first seal that extends        simultaneously against said faces in order to close off a first        passage between the annular support and the cover, thereby        preventing the aerosol sucked in via the tunnel from bypassing        the filter membrane, whereas a second seal positioned between        the cap and the cover to close off a second passage between the        base and the cap prevents any aerosol that may be sucked up by a        passage between the base and the cap from combining with the        aerosol sucked in via the tunnel;    -   it makes the filtration assembly easier to handle. Specifically,        the filtration assembly can be grasped via the peripheral        external face of the skirt, for example using grippers.

For preference, the skirt and the ring of the cover are formed as onematerial.

The invention also relates to a removable cassette for an apparatus forsampling nanoparticles, the cassette comprising:

-   -   a base comprising means for securing it to a nanoparticles        sampling apparatus and a cap that fits onto the base and that        with the base defines a tunnel having an inlet open to the        outside and an outlet that can be fitted with a fluidtight seal        to a suction inlet of the sampling apparatus;    -   a filtration assembly as explained hereinabove, sandwiched        between the base and the cap;    -   a first seal positioned so that it extends simultaneously        against said faces so as to close off a passage between the        annular support and the cover, and a second seal positioned        against the cover so as to close off a passage between the base        and the cap.

According to one particular embodiment of the invention, the two sealsare flat seals positioned one either side of the filtration assemblybefore it is sandwiched between the base and the cap.

According to one particular embodiment of the invention, the skirt endsin a reinforcement able to allow the cover to be clip-fastened onto theannular support when the cover is attached to the annular support. Thus,the filtration assembly can easily be handled by being held by theskirt, without the risk of this skirt sliding the annular support.

DESCRIPTION OF THE FIGURES

The invention will be better understood in the light of the followingdescription of one particular exemplary embodiment of the invention,given with reference to the attached drawings among which:

FIG. 1 is a partial perspective view of a sampling apparatus equippedwith a removable cassette;

FIG. 2 is an exploded perspective view of a removable cassette accordingto the invention;

FIG. 3 is a view in part section of the removable cassette of FIG. 2;

FIG. 4 is an enlarged view of FIG. 3;

FIG. 5 is a view similar to FIG. 4 of an alternative form of embodimentof the cassette of the invention;

FIG. 6 is a cross section through a first seal that can be used in thecassettes of FIGS. 2 to 5.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS OF THE INVENTION

With reference to FIG. 1 and as is known per se, the invention is aimedmore particularly at a removable cassette 1 that can be fitted to asampling apparatus 2 equipped with suction means for sucking an aerosolthrough a tunnel formed in the cassette 1. As illustrated in FIG. 2, theremovable cassette 1 comprises a base 3 to which a cap 4 is attached (inthis instance by clip-fastening) so that these between them trap afiltration assembly 5.

As illustrated in FIGS. 3 and 4, the base 3 and the cap 4 exhibitsymmetry of revolution and internally define a tunnel 6 which extendsfrom an inlet 7 protected by a guard 8 which has a hole at the inlet 7as far as an outlet 9 which fits into an inlet 10 of the suction meansof the sampling apparatus 2. The tunnel 6 is completely barred by afilter membrane 11 of the filtration assembly 5. Thus, the aerosolsucked in by the sampling apparatus enters the tunnel 6 via the inlet 7and emerges via the outlet 9 having passed through the filter membrane11 which retains the nanoparticles in suspension in the sucked-inaerosol. The removable cassette 1 is attached by any known means(clip-fastening, screwing, etc.) that allows it to be removed so thatthe nanoparticles captured and retained by the filter membrane 11 can beanalyzed. All of this is perfectly well known and is recalled only toillustrate the invention.

The filtration assembly 5 comprises an annular support 12, for examplemade of polyamide, which comprises an annular step 13 which projectsfrom a planar face 14 of the annular support 12 to exhibit an apex 15 onwhich the filter membrane 11 can rest. The filter membrane 11 extendsbeyond the apex 15 so as to rest on the planar face 14. The annularsupport 12 is covered by a cover 20, for example made of polycarbonate,which comprises a ring 21 attached to the annular support 12 to sandwichthe filter membrane 11 between the ring 21 and the external face of thestep 13. For that purpose, the cover 20 is force-fitted so as tosandwich the filter membrane 11 and pull it taut so that it then forms aplanar surface suitable for subsequent analysis. The ring 21 also trapsa peripheral part of the filter membrane 11 resting on the planar face14 of the annular support 12. According to the invention, the ring 21 isextended by a skirt 22, here formed of one material with the ring 21,which extends in such a way as to cover a peripheral face of the annularsupport 12 and extends as far as an end face 23 which extends in thecontinuation of a bearing face 24 of the annular support, on theopposite side to the planar face 14 on which the filter membrane 11rests.

In this instance, the skirt 22 ends in a peripheral reinforcement 25exhibiting a slight undercut that collaborates with a chamfered part 26of the annular support 12 to allow the cover 20 to be clip-fastened ontothe annular support 12 when the filtration assembly 5 is being fitted.During fitting, the reinforcement 25 has to be forced around theperipheral face of the support 12 and the cover 20 has to be slid aroundthe annular support 12 until the reinforcement 25 clips around thechamfered part 26 of the annular support 12. For preference, theclip-fastening causes the ring 21 to press against the bearing face 14of the annular support. The assembly can therefore be handled easily,holding it by the skirt 22, for example using the gripper of a robotarm.

When the filtration assembly 5 is being fitted in the removable cassette1, a first seal 30, in this instance a flat seal made of elastomer, isinterposed and extends firstly against a planar face 32 of the base 3and secondly and at the same time against the end face 23 of the skirt22 and against the bearing face 24 of the annular support 12. The firstseal 30 closes any passage that might be between the annular support 12and the cover 20, thus preventing the membrane 11 from being bypassedusing this passage.

Furthermore, a second seal 33, in this instance a flat seal made ofelastomer, is interposed and extends against a planar face 34 of the cap4 and a bearing face 35 of the ring 21. The second seal 32 eliminatesany possibility of aerosol sucked up via a space between the base 3 andthe cap 4 from being able to combine with the aerosol sucked up via theinlet 7 of the tunnel 6.

The seals are of course squashed when the cap 4 is clip-fastened ontothe base 3. As an alternative illustrated in FIG. 5, the second seal 33in this instance is replaced by an O ring seal 36 housed in an annulargroove of the cap 4 so that it bears against an external face of theskirt 22. This O ring seal has the same effect as the flat seal that itreplaces.

The invention is not restricted to that which has just been describedbut rather encompasses any alternative form that falls within the scopedefined by the claims.

In particular, although in the examples illustrated the removablecassettes are provided with a second seal, the latter may be omitted ifthe base and the cap are designed so that, when assembled with oneanother, they obstruct in a sealed manner any passage between them, forexample via the interposition of a seal between these two elements.

Although in the examples illustrated the skirt is formed of one materialwith the ring, a two-part cover may be anticipated. In particular, theskirt could be made from a softer material than the ring, making iteasier to clip-fasten onto the annular support. In that regard, althoughhere the clip-fastening means for clip-fastening the skirt onto theannular support comprise an end reinforcement with an undercut of theskirt collaborating with a chamfered part of the annular support, anyother clip-fastening means, preferably ones which cause the ring to bepressed against the face of the annular support against which the filtermembrane 11 presses may be provided.

Finally, the seals used may be of any possible shape. In particular, asillustrated in FIG. 6, the first seal 30 may have annular bulges 35pressing respectively against the end face of the skirt and the bearingface of the annular support.

1. A filtration assembly for halting and retaining nanoparticles insuspension in an aerosol passing through the filtration assembly, thefiltration assembly comprising an annular support which comprises anannular step having an apex on which a filter membrane rests, and acover covering the annular support to hold a periphery of the membranebetween the cover and the annular support, characterized in that thecover comprises a ring that can be slipped around the step to sandwichthe periphery of the membrane between the ring and the annular support,the ring being extended by a skirt which projects out from the ring tocover an external peripheral wall of the annular support and to have anend face which extends in continuity with a bearing face of the annularsupport.
 2. The filtration assembly as claimed in claim 1, in which thering and the skirt of the cover are formed in one material.
 3. Thefiltration assembly as claimed in claim 1, in which the skirt ends inmeans for clip-fastening onto the annular support.
 4. The filtrationassembly as claimed in claim 3, in which the clip-fastening meanscomprise an annular reinforcement exhibiting an undercut intended tocollaborate with a chamfered part of the annular support.
 5. A removablecassette for an apparatus for sampling nanoparticles, comprising a basethat can be fitted removably onto the filtration apparatus, and a capattached to the base to trap a filtration assembly as claimed inclaim
 1. 6. The removable cassette as claimed in claim 5, comprising afirst seal positioned between the base and the filtration assembly toextend simultaneously against the end face of the skirt and the bearingface of the annular support.
 7. The removable cassette as claimed inclaim 6, in which the first seal is a flat seal made of elastomer. 8.The removable cassette as claimed in claim 5, comprising a second sealpositioned between the cap and the cover of the filtration assembly. 9.The removable cassette as claimed in claim 8, in which the second sealis a flat seal made of elastomer positioned in such a way as to bearagainst a flat face of the ring of the cover.
 10. The removable cassetteas claimed in claim 8, in which the second seal is an O ring sealpositioned in such a way as to bear against an external face of theskirt of the cover.